1. Field of the Invention
The present invention relates to an image print technique.
2. Description of the Related Art
In recent years, image printing devices having a borderless print function of printing an image on the full surface of a sheet upon printing image data captured by a digital camera, a portable phone with a camera, and the like are increasing, and demand for borderless printing are increasing.
Since the performance of image reading devices has improved, demand for reading a printed image using an image reading device such as a copying machine or scanner, and printing the read image again are also increasing.
Furthermore, demand for reading an image of a borderless-printed sheet using an image reading device, and borderless-printing the read image again are increasing.
A method of executing borderless-print processing using a conventional image printing device, reading an image of a borderless-printed sheet using an image reading device, and borderless-printing the read image again will be described below.
Upon execution of borderless-print processing using a conventional image printing device, a maximum image size printable on the full surface of a print sheet is calculated based on the size of the print sheet and a resolution. Then, a size slightly larger than the maximum image size printable on the full surface of the sheet is set as an output image size. An input image is enlarged or reduced to fit the output image size. As shown in FIG. 4, an output image 42 is printed so that a print sheet 41 is located inside the output image 42, thus realizing the borderless-print by creating a state in which no non-printed part is formed on the print sheet 41.
For example, when resolution is expressed by dpi (dots per inch), and a case will be explained below wherein the size (vertical×horizontal) of an input image is 1600×1200 dots, the size (vertical×horizontal) of a print sheet is 4×3 inches, and the resolution is 600 dpi. The maximum image size printable on the full surface of the print sheet is 2400×1800 dots by multiplying the size of the print sheet by the resolution. Assuming that an output image size (vertical×horizontal) is obtained by adding 20 dots to the maximum image size printable on the full surface of the print sheet in both the vertical and horizontal directions, it is 2420×1820 dots. Therefore, processing for enlarging the input image to exceed 2420×1820 dots is executed. This enlargement processing uses interpolation processing, such as linear interpolation processing, to have the same enlargement ratios in the vertical and horizontal directions, and executes interpolation processing so that 1600×1200 dots exceed 2420×1820 dots. In the aforementioned case, the input image is enlarged in correspondence with the enlargement ratio (1820/1200 times) of the short side, thus generating an output image of 2427×1820 dots. The print sheet is set at a position where it falls inside the output image, and the borderless-print processing is executed so that the output image is partially deleted.
When an image of the borderless-printed print sheet is read by a conventional image reading device, and the borderless-print processing of the read image is executed again, the borderless-printed print sheet is converted into image data using an image sensor. The read image data is stored in a memory. Then, a method of executing borderless-print processing using the conventional image printing device again to have the image data stored in the memory as an input image is available.
For example, when an image of a print sheet borderless-printed by the conventional image printing device is read at a read resolution of 600 dpi, the size of the read image data is 2400×1800 dots. Upon execution of the borderless-print processing again, the read image data (having the size of 2400×1800 dots) is used as an input image. In the conventional image printing device, the output image size is set to be slightly larger than the maximum image size printable on the full surface of the print sheet. Therefore, the output image size (vertical×horizontal) is set to be 2420×1820 dots. Then, the read image data undergoes enlargement processing for enlarging it to image data of a size larger than 2420×1820 dots, thus generating an output image. A print sheet is set at a position where the print sheet falls inside the output image, thus implementing the borderless-print processing again so that the output image is partially deleted.
However, when borderless-print processing is executed again using the borderless-printed print sheet using the conventional image printing device and image reading device, the first borderless-printed result is different from the second borderless-print result. Such difference will be described below with reference to FIGS. 7A to 7C and FIGS. 8A to 8C. FIGS. 7A to 7C are views for explaining the processes of the first borderless-print processing using the conventional image printing device. FIGS. 8A to 8C are views for explaining the processes of the second borderless-print processing using a borderless-printed image by the conventional image printing device.
FIG. 7A shows an original image (input image) used in the first borderless-print processing. FIG. 7B shows an image 72 obtained by converting the original image into an image of a size larger than a print sheet 71, and the print sheet 71. FIG. 7C shows a result obtained when only a region of the image 72 that overlaps the print sheet 71 is printed on the print sheet 71.
FIG. 8A shows an input image used in the second borderless-print processing. This input image is obtained by reading an image of the print sheet as the print result shown in FIG. 7C using the image reading device, extracting only a print sheet part of the read image, and converting the extracted print sheet part into image data. FIG. 8B shows an image 82 obtained by converting the input image into an image of a size larger than a print sheet 81, and the print sheet 81. FIG. 8C shows a result obtained when only a region of the image 82 that overlaps the print sheet 81 is printed on the print sheet 81.
In the first borderless-print processing, the original image shown in FIG. 7A is received, and is enlarged to the image 72 of a size larger than the print sheet 71. Then, the print sheet 71 is aligned to fall inside the enlarged image 72, and the positional relationship between the image 72 and print sheet 71 is set in the state shown in FIG. 7B. Then, the image 72 is printed after a region outside the print sheet 71 and inside the image 72 is deleted, thus obtaining the print result shown in FIG. 7C.
In the second borderless-print processing using a borderless-printed image, an image (FIG. 8A) obtained by reading a print sheet on which the print result shown in FIG. 7C is printed as the first borderless-print result is read by the image reading device and is used as an input image. Then, this input image is enlarged to the image 82 of a size larger than the print sheet 81. The print sheet 81 is aligned to fall inside the image 82, and the positional relationship between the image 82 and print sheet 81 is set in the state shown in FIG. 8B. Then, the image 82 is printed after a region outside the print sheet 81 and inside the image 82 is deleted, thus obtaining the print result shown in FIG. 8C.
Therefore, as can be seen from the print results shown in FIGS. 7C and 8C, the first borderless-print result is different from the second borderless-print result, thus posing a problem.
In order to solve this problem, a technique which embeds only a region to be deleted using a digital watermark technique has been proposed (Japanese Patent No. 3554753). According to Japanese Patent No. 3554753, a region to be partially deleted is set on an input image. Then, an edit image is obtained by deleting the set region from the input image. The image of the set region is compressed and is embedded in the edit image. After that, the edit image is output.
When the borderless-print processing is executed again using a borderless-printed sheet to obtain the same borderless-print image by the aforementioned method, data to be deleted by the borderless-print processing has to be embedded in advance in the borderless-printed sheet. Then, the image reading device reads a borderless-printed image to restore the embedded “data to be deleted by borderless-print processing”. Image data obtained by reading the borderless-printed image is merged with the restored “data to be deleted” to restore an input image before the borderless-print processing. When the restored input image is borderless-printed again, a borderless-printed image having the same size can be obtained.
However, in the aforementioned conventional method, a region to be deleted at the time of the borderless-print processing has to be set in advance. However, in a printer in which the user places a print sheet on a document table to execute print processing, it is easy to assume that the position where the print sheet is to be placed is easily shifted. Therefore, since it is assumed that the region to be deleted at the time of the borderless-print processing is also easily shifted, it is difficult to set the region to be deleted in advance. Such difficulty will be described below with reference to FIGS. 9A to 9C and FIGS. 10A to 10C.
FIGS. 9A to 9C are views for explaining a case in which a print region which is set in advance upon execution of borderless-print processing matches that in the borderless-print result. FIG. 9A shows an input image which is input to be borderless-printed. FIG. 9B shows an image 92 obtained when the input image is converted into the image 92 having a size larger than a print sheet 91, and the print sheet 91. The print sheet 91 also shows a print region which is set in advance. FIG. 9C shows a result obtained when only a region of the image 92 that overlaps the print sheet 91 is printed on the print sheet 91.
FIGS. 10A to 10C are views for explaining a case in which a print region which is set in advance upon execution of borderless-print processing does not match that in the borderless-print result. FIG. 10A shows an input image which is input to be borderless-printed. FIG. 10B shows an image 102 obtained when the input image is converted into the image 102 having a size larger than a print sheet 101, and the print sheet 101. Since the print sheet 101 is placed at a shifted position, the positional relationship with the image 102 is different (shifted) from that between the image 92 and print sheet 91 shown in FIG. 9B. FIG. 10C shows a result obtained when only a region of the image 102 that overlaps the print sheet 101 is printed on the print sheet 101.
FIGS. 9A to 9C and FIGS. 10A to 10C show the case free from any positional shift of the print sheet and the case that suffers a positional shift when the same input image is input and is borderless-printed using printers having the same print performance. As can be seen from the print results shown in FIGS. 9C and 10C, different print results are obtained due to the positional shift of the print sheet.
Assume that a printed print sheet is read using the image reading device, additional information is extracted from the read image, and the extracted information is restored. This additional information indicates a delete region which is set in advance. In this case, a case will be described below wherein an original image cannot be restored by compositing the read image and an image of the restored delete region which is set in advance.
FIGS. 11A to 11C are views for explaining an example in which a document, which is printed on a print sheet whose position is shifted, is read, additional information is extracted from the read document image to restore an image, and the restored image and the read document image are composited.
The additional information indicates a delete region which is set in advance, i.e., a region obtained by excluding a region of the print sheet 91 from that of the image 92 shown in FIG. 9B. Assume that an input image before being printed on a print sheet whose position is shifted is the image 102 shown in FIG. 10A, and a print sheet which has undergone the print processing with the print sheet position shifted is the print result shown in FIG. 10C.
FIG. 11A shows an image as a result of reading a print sheet which has undergone the borderless-print processing with the print sheet position shifted using the image reading device. FIG. 11B shows an image as a result of extracting additional information from the image shown in FIG. 11A, and restoring the additional information. FIG. 11C shows an image as a result of compositing the image shown in FIG. 11A and that shown in FIG. 11B.
As can be seen from the result shown in FIG. 11C, the input image (FIG. 10A) before the borderless-print processing cannot be restored.
Therefore, when the position of a print sheet is shifted even slightly from a delete region which is set in advance, even when data of only the region to be deleted is saved, it is very difficult to restore an input image before the borderless-print processing. When the embedded delete region is restored and is composited with an image read using the image reading device, it is difficult to composite these images by aligning them in a state in which the delete region which is set in advance is shifted.